The exiting cable company ground block is on the opposite side of the house, where the electrical service, phone and cable is grounded. My antenna is mounted on the opposite side of the house.

I have installed my 75' of coax through the attic down by the chimney to close to the circuit breaker panel. From there I mounted a grounding block and grounded it, with 10 gauge solid copper wire, to a grounding cable that goes from my water pipe to the panel.

My antenna mast is EMT and I have grounded it, with 10 gauge solid copper wire, to a 4' copper grounding rod below the mast.

Can I run my 75' coax through my attic into my cellar and ground it to the ground wire going from my water pipe to my circuit panel?

Or should I ground the coax from a grounding block to the grounding rod before it enters the house and is stung through the attic? If so, would I need to ground the grounding rod to the ground on the other side of the house too?

The NEC does not prohibit running the antenna system grounding/bonding conductor through the building structure. For what it's worth, my personal preference is to avoid doing so... Why would I invite fault current into or through my home?

I believe that it's best to ground the mast and coax outside at the electrical service, like the phone and cable service. Grounding the mast with an isolated rod in the earth fails to accomplish the ultimate goal of reducing the chance of harm to people and property in the event of a fault. If you opt to add a ground rod, the NEC requires that it be bonded to your existing electrical system using #6 AWG copper or better, and approved connectors and methods.

That's an option that conforms to the NEC... You simply need to use #6 AWG or better copper and the appropriate connectors to bond the axillary ground rod to the existing electrical service grounding system. In most installations, the ground rod alone, provides very little added protection... It's the heavy bonding conductor that is capable of holding the various grounded items at the same voltage level during a fault. Preventing voltage differences between conductive surfaces is the goal.

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If the well is dry and you don't see rain on the horizon, you'll need to dig the hole deeper. (If the antenna can't get the job done, an amp won't fix it.)